Q22 / 124 · NTA Abhyas (JEE Main) 2020 · Mathematics · Determinants

If A, B are two non-singular matrices of order 3 and I is an identity matrix of order 3 such that AAT=5Ι and 3A-1=2AT-Aadj4B, then B2 is equal to (where AT and adjA denote transpose and adjoint matrices of the matrix A respectively)

  • Correct answer
    A
    7353⋅46
  • B
    7353⋅43
  • C
    7453⋅212
  • D
    5673⋅210

Solution

AAT=5Ι⇒A2=53 ….(1)
3A-1=2AT-adj4B
Multiplying by A on both sides, we get
3Ι=2AAT-Aadj4B
⇒A2adj4B=7Ι
A2adj4B=73
5346B2=73 (using (1))
B2=7353⋅46

Hence, the correct answer is option: 'A'.

More Determinants Questions